Method of assembling fuse links



INVENTOR.

2 Sheets-Sheet 1 C. W. BROWN METHOD OF ASSEMBLING FUSE LINKS Flled July 27, 1942 Dec. 17, 1946,

Dec. 17, 1946. c, w BROWN I 2,412,712

METHOD OF ASSEMBLING FUSE LINKS Filed July 27, 1942 2 Sheets-Sheet 2 Patented Dec. 17, 1946 METHOD OF ASSEMBLIN G FUSE LINKS Chester W. Brown, Milwaukee, Wis., assignor to Line Material Company, Milwaukee, Wis., a

corporation of Delaware Application July 27, 1942, Serial No. 452,436

6 Claims.

This invention relates to the production of spring fuse-links of the type and species illustrated and described in Steinmayer U. S. Patent No. 2,270,225; and it has to do with an improved method of manufacture, and particularly a more facile and speedy method of assembling the component parts of such fuse-links. The object, of course, is to effect a reduction of manufacturing cost.

In the drawings which accompany this specification Figs. 1 to 7, inclusive, illustrate successive oprations or steps in the course of assembly of a fuse-link, conformably to the present invention;

Fig. 8 is a sectional view of a flattening die, taken along the line 8-8 of Fig. '7

Fig. 9 is a sectional view of the flattening die taken along the line 9-9 of Fig. 8; and

Fig. 10 is an elevational view, partly in section, of a completed fuse-link. 1

Fig. 11 is an enlarged sectional view take along the line I l-I l of Fig. 10.

It is believed most expedious to describe first the completely assembled fuse-link shown in Fig. 10 and, thereafter, to proceed step-by-step with a description of the assembling operations.

Referring to Fig. 10, the fuse-link shown comprises a fibre protector tube l2, an upper terminal member I 3, a fusible section l4, and expulsion spring 15, a nut 16, and a flexible leader [1.

Terminal member I 3 includes a conventional button-head contact l3a, a tubular shank portion which is flattened at 13b from just below the button head contact to just above the upper end of protector tube 12. Portion I30 of the terminal member is not flattened but is deformed, as shown in cross-section in Fig. 4, to grip the upper ends of. a strain wire 18 and a fuse wire l9 constituting fusible section [4. Portion I30 is, in the main, cylindrical and a close fit in the bore of protector tube I2.

The lower ends of strain wire it and fuse wire H! are soldered to the adjoining end of flexible leader H.

The upper end of expulsion spring i is constricted to form an abutment for the upper end of the leader; and nut l8 functions to anchor the lower end of the spring and normally retain it under tension. The strain wire normally is under a predetermined tension effected by the ex pulsion spring, and, in event the fusible section blows, the leader is quickly expelled from the tube by the spring. The fuse-link structure just described is substantially identical with the disclosure of the above mentioned Steimnayer Patent No. 2,2'70,225tl1e sole novelty residing in the improved manufacturing method which now will be explained.

The first step-of the assembling operation is illustrated in Fig. l and consists in soldering or otherwise securing to one end of leader I 1 the strain wire 18 and fuse wire lflthe latter being twisted around the strain wire as shown.

The second step is illustrated in Fig. 2 nd consists merely in adding spring E by threading therethrough the strain wire and fuse wire.

The third step, depicted in Fig. 3, consists in inserting the free ends of the strain wire and fuse wire into the tubular shank of terminal member is and locally prick-punching said shank at 13d in the manner portrayed in the crosssectional detail Fig. 4. This results in firmly anchoring the strain and fuse wires to the shank of the terminal member.

The fourth step consists in inserting the assembly of Fig. 3 into tube it as illustrated in Fig. 5.

The fifth step consists in screwing nut I6 onto the lower end of spring l5 as depicted in Fig. 6.

Thereafter, as a sixth and final step, terminal member I3 is pulled longitudinally and outwardly of tube 12 and the tubular shank portion is fiattened at [312, as shown in the cross-sectional view, Fig. 11. The flattening of the shank is effected in a pres (not shown) by means of a punch 29 and dies or anvil 2i shown in Figs. 7, 8, and 9. The punch is a simple metal flattening tool, the working end of which only is illustrated. The upper portion of the punch is, of course, secured to the ram of the press. Die 2i comprises a base portion 2m which is secured in any appropriate manner to the bed or platen of the press in proper alignment with the punch. Forming an integral part of and projecting upwardly from the base portion of the die is a pad 2| b having a finished top surface. At one end of pad Zlb is a pair of spaced upwardly extending ears 22 and 23 which may be welded or otherwise secured to the base. The spacing between the latters ears is sufiicient to clear and permit insertion therebetween of the portion l3e of buttonhead contact lsa. t the other extremity of pad 2|b are disposed a second pair of spaced upstanding ears 2-! and 25. These are aligned with cars 22 and 23 respectively and the spacing between them is such as to clear the tubular shank portion I32).

The extent to which tubular shank portion l3c extends into the bore of tube 2 and, incidentally, the tension applied to spring I5 is determined by the separation, longitudinally of the fuse-link, between the pair of cars 22, 23 and the pair of cars 24, 25. The latter are beveled at 24c and 25a so that the flowing metal resulting from the flattening operation will not make it diflicult to remove the fuse-link from the die. A knock-out for ejecting the fuse-link from the die may be employed if desired. This is in keeping with well-known die-making practice and needs no illustration.

3 What is claimed is: l. The method which includes the following enumerated steps: (1) making a sub-assembly comprising a relatively elongate terminal memher, a fusible section connected at one end only to one end of said terminal member, a conductive eader connected at one end only to the other end only of said fusible section, and a helical spring anchored at one end only to said conductive leader and extending, from its anchorage, along said leader and co-axially therewith and away from said fusible section; (2) inserting telescopically into the bore of a protector tube and adjacent the end of said tube from which it projects to form a stop engaging said tube for maintaining said spring under tension.

2. Ihe method which includes the following enumerated steps: (1) making a. sub-assembly comprising a relatively elongate terminal memher, a fusible section connected at one end only to one end of said terminal member, and a helical spring connected at one end only with the other end of said fusible section; (2) inserting telescopically into the bore of a protector tube the sub-assembly of the first step so that the terminal member extends into one end oi the tube while the free end of the spring projects out of the other end of the tube; (3) anchoring the aforementioned free end of the spring to the end of the tube adjacent thereto; (4) applying tensile force axially to said terminal member in a direction to eiTect tensioning of said spring and resultantly to efiect a predetermined partial withdrawal of said terminal member from the bore of the tube and; (5) compressing said terminal member laterally to form one or more shoulders thereon immediately adjacent the end of said tube to prevent contraction or said spring and thereby normally to maintain said spring under tension.

3, The method which includes the following enumerated steps: (1) making a sub-assembly comprising a relatively elongate terminal member, a fusible section connected at one end only to one end of said terminal member, and a hellcal sprin connected at one end only with the other end of said fusible section; (2) inserting telescopically into the bore of a protector tube the sub-assembly of the first step so that the terminal member extends into one end of the tube while the free end of the spring projects out of the other end of the tube; (3) attaching the projecting free end of the spring to a nut for anchoring the spring to the end of the tube adjacent thereto; (4) applying tensile force axially to said terminal member in a direction to effect tensioning of said spring and resultantly to effect a predetermined partial withdrawal of said terzrinalmember from the bore of the tube and; (5) flattening the terminal member outside the bore. of said tube and immediately adjacent the end thereof to form stop means for normally retaining said spring under tension.

4. The method which includes the following enumerated steps: (1) attaching end to end a flexible conductive leader and a fusible section comprising a'fuse wire and a strain wire in parallel; (2) adding to the assemblage of step (1) a helical spring encircling the conductive leader and having one end anchored to the junction between the conductive leader and fusible section, said spring extending from said junction away from said fusible section; (3) inserting the end of said fusible section remote from said conductive leader into one end of an elongate tubular terminal member and prick-punching said tubular terminal member laterally to grip the inserted end of the fusible section; (4:) inserting telescopically into the bore of a protector tube the assemblage resulting from the three aboveenumerated steps so that the tubular terminal member extends into one end ofthe protector tube while the end of the spring remote from the fusible section is outside the other end of the protector tube; (5) anchoring the last-mentioned end of the spring to that end of the protector tube which is remote from said tubular terminal member; (6) applying tensile force axially to said terminal member in a direction to sheet tensioning of said spring and resultantly to effect a partial withdrawal of said terminal member from the bore of the protector tube and; (7) flattening said terminal member outside the bore and adjacent that end of the protector tube from which it projects to form a shoulder engaging the last-mentioned end of the protector tube for maintaining said spring under tension.

5. The method of tensioning a fuse link comprising a terminal, a. leader, and a strain section mechanically and electrically connecting said terminal and leader and including a coil spring surrounding said leader and anchored thereto adjacent said section; said method comprising, first, the mounting of a tube on said leader and moving it to a position embracing said terminal, strain section, and a portion of said spring; second, the mounting of a nut on the projecting end of said spring; third, the moving of the tube to cause expansion of said spring axially; and, fourth, the deforming of said terminal to provide tube engaging means for holding tle tube in spring expanded position.

6. The method of assembling a spring tensioned fuse link, said method comprising in sequence as follows: first, securing a flexible cable and strain wire together in end to end relation; second, passing the strain wire and a portion of the cable through a coil spring and engaging one end of the spring with the juncture between said cable and wire; third, passing the nd of said wire remote from said cable into a tubular terminal and deforming the end of the latter nearest said cable to secure it to the wire; fourth, passing the cable, spring, wire, and terminal through a protectivetube until a portion of the spring is exposed at the trailing end of said protective tube; fifth, passing'said cable through a nut and screwing said out upon the exposed end of said spring; sixth, pulling the major portion of said terminal from said protective tube and coincidental therewith stressing said spring through the medium of said protective tube and nut; and seventh, flattening the exposed. intermediate portion of said terminal to spread it laterally into position for endwise engagement with said protective tube.

CHESTER W. BROWN. 

